Nozzle shut-off and flow control valve

ABSTRACT

A combined nozzle shut-off and flow control valve for use with a plastic molding machine is disclosed comprising a valve body having a bore communicating with outlet passage means of reduced diameter and axially aligned with said bore and radial inlet passage means; a valve stem, having an inner axial passage, axially positioned within said bore and capable of relative axial movement therein; nozzle valve rod means slidably positioned in said valve stem inner axial passage and aligned to register in to effect closure of said outlet passage means; the lower surfaces of said bore and said valve stem having parallel annular surfaces providing a gap of variable width to effect flow control through said valve.

finite States Patent [191 Geist 1 Dec. 25, 1973 [75] Inventor: RobertJoseph Geist, lsla Verde,

[73] Assignee: Union Carbide Corporation, New

York, NY.

[22] Filed: Apr. 7, 1.972

[21] Appl. No.: 242,177

[52] US. Cl. 137/613, 425/245 [51] Int. Cl 329i 1/00 [58] Field ofSearch 137/613, 170.1;

[56] References Cited UNITED STATES PATENTS 3,095,609 7/1963 Lievre425/245 2,865,050 12/1958 Strauss ..425/245X FORElGN PATENTS ORAPPLICATIONS 1,274,579 9/1961 France 425/245 Primary ExaminerSamuelScott Assistant Examiner-Ira S. Lazarus Atlorney-Paul A. Rose et all[57] ABSTRACT A combined nozzle shut-off and flow control valve for usewith a plastic molding machine is disclosed comprising a valve bodyhaving a bore communicating with outlet passage means of reduceddiameter and axially aligned with said bore and radial inlet passagemeans; a valve stem, having an inner axial passage. axially positionedwithin said bore and capable of relative axial movement therein; nozzlevalve rod means slidably positioned in said valve stem inner axialpassage and aligned to register in to effect closure of said outletpassage means; the lower surfaces of said bore and said valve stemhaving parallel annular surfaces providing a gap of variable width toeffect flow control through said valve.

3 Claims, 3 Drawing Figures PATENTEUBEEZS 191a 3.780.764

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A VALVE FIXED VALVE FI G.3.

NOZZLE SHUT-OFF AND FLOW CONTROL VALVE The present invention relates tonozzle shut-off and flow control valves employed in machines for theinjection and blow molding of thermoplastic materials. Current injectionand blow molding machine nozzle shutoff and flow control valves areseparate units. The need exists for a more compact arrangement combiningthe separate nozzle shut-off and flow control valve into a more compactand streamlined single unit.

In accordance with the present invention, a combined nozzle shut-off andflow control valve for use with a plastic molding machine is providedcomprising: a valve body having a bore communicating with outlet passagemeans of reduced diameter and axially aligned with said bore and radialinlet passage means; a valve stem, having an inner axial passage,axially positioned within said bore and capable of relative axialmovement therein; nozzle valve rod means slidably positioned in saidvalve stem inner axial passage and aligned to register in to effectclosure of said outlet passage means; the lower surfaces of said boreand said valve stem having parallel annular surfaces providing a gap ofvariable width to effect flow control through said valve.

In the valve of the present invention the fluid flows between twoparallel or near parallel surfaces each of which exert a frictional dragon the fluid. The extent to which the drag restricts the fluid flowdepends upon the length of the surface and clearance between thesurfaces. This action is in addition to the restriction of the size ofthe opening through which the fluid must flow. When a fluid flows over asurface, the fluid in contact with the surface may be assumed to bestationary. There have been reported cases of slip at the surface, butthese have been the exception to the rule. A statonary fluid at thesurface is assumed for both parallel surfaces of the valve. Although thevelocity of the fluid at the surface is zero, it increases as thedistance from the surface is increased. In the case of the valve of theinvention, the maximum is in the center between the two parallelsurfaces. As the surfaces are brought closer together, the averagevelocity is reduced.

The volume of fluid that can pass between the two surfaces is a functionof the area perpendicular to the flow through which the fluid flows andthe average velocity of the fluid. As the two surfaces are broughtcloser together, the area through which the fluid must flow decreasesand the average velocity also decreases. Therefore, during the sameamount of time less fluid will pass between the surfaces.

In a structural foam injection molding this is important when more thanone nozzle and valve are used simultaneously. The nozzlevalve-combinations are connected together on a parallel arrangement sothat they may be fed off a common feed line. With this arrangement, timeis not important but the fact that one nozzle-valve combination has agreater restriction to flow than another will cause more foamed plasticto exit the nozzle with the lesser restriction. This permits, forexample, molding a 2 pound part from one nozzle while simultaneouslymolding a pound part from another nozzle. Prior efforts at making acompact unit, such as typified by the unit of U.S. Pat. No. 3,561,062,only restrict the size of the opening through which the fluid must passfrom the manifold into the nozzle.

In the drawings:

FIG. 1 is a sectional view of a valve embodying the present invention;

FIG. 2 is a sectional view of another embodiment of valve embodying theinvention; and

FIG. 3 is a series of curves showing the flow control comparativeperformance of a valve of the present invention and one of the priorart.

In the embodiment of valve as shown in FIG. 1, manifold 10 containscommon feed passage 12. The usual nozzle 13 is shown having circularnozzle passage 14. The valve consists of an axially aligned valve stem16 positioned in a closed bore in the valve body and having annular landsurface 18. A parallel annular surface 20 is also machined into thevalve body. By adjusting the valve stem 16 up or down, as by rotation onthreads or the like, the gap width can be variably adjusted. The twoparallel surfaces, 18 and 20, are the surfaces mentioned above in thediscussion of the valve principle. Nozzle rod 24 passes through thevalve stem and is concentric with it. Actuated by external means, nozzlerod 24 slides in valve stem 16 and is shown in the shut-off positionwhich does not permit material to flow through the nozzle passage 14. Byretracting the rod from nozzle passage 14, the flow of materialcommences and the nozzle is thus open.

In operation, when nozzle rod 24 is retracted from nozzle passage 14,the material flows from manifold passage 12 through inlet passage 26 andinto annular chamber 28 in the valve body. The material passes aroundvalve stem 16 and through the gap 22 where the throttling or flowcontrol takes place. It then passes through nozzle passage 14, throughnozzle and into the mold. When the desired volume of material has beeninjected into the mold, the nozzle rod is passed into passage 14 closingthe nozzle. Once the valve stem is adjusted to the proper flow control,it remains in that position and is not changed for each molding cycle.This is in contrast to the nozzle rod which moves in and out of thenozzle passage for each molding cycle. By adjusting the valve stem, thesize of the gap 22 between the parallel surfaces, 18 and 20, may bechanged and the flow through valve may be altered.

The angle of the land of the valve stem and parallel surface of thevalve body is not believed to be critical. A large angle requires lessmovement of the valve stem for a given amount of gap change than does asmaller angle. For the same land length, a shallow angle results in aless bulky valve stem and less bulky valve assembly. The amount that thebulk is reduced is small. Again, for the same land length, a shallowangle reduces the ratio of the inlet area to the outlet area of thevalves.

In the embodiment shown in FIG. 2 of the drawing, nozzle rod 24 andvalve stem 16 pass through the manifold common feed passage 12. Thisembodiment is believed to offer better streamlining. In other respects,its structure and operation is the same as that of the embodiment ofFIG. 1.

Although the structural foam injection molding process does not requiremultiple nozzles, the typical structural foam machine, as described inU.S. Pat. Nos. 3,268,636 and 3,436,446, uses them to inject foamedplastic into molds. These nozzles are grouped together into at least onemanifold. This manifold contains a passage that feeds the plastic to thenozzles and the nozzles branch from that passage. Current practiceplaces throttle valves between the manifold passage I and each nozzle.When more than .one nozzle is needed, the throttle valves are used toregulate the quantity of material that flows out of each nozzle beingused. Thus, if a part or parts with a total weight of ten pounds arebeing molded, the valves can be adjusted so that two pounds existsthrough one nozzle, three pounds through another and five pounds througha third nozzle. There is no limit to the number of nozzles that may beused. The manifold is fed by an accumulator which is, in turn, fedfoamed plastic by an extruder. The accumulator displaces an adjustablecontrolled volume of material. Unless the valves are all fully closed,the accumulator will force the same amount of foamed plastic out of themachine regardless of the settings on the throttle valves. Adjusting thethrottle valve alters the distribution of the foamed plastic but not thetotal amount molded.

As shown in the curves of FIG. 3 of the drawings, the relationshipbetween the percentage change in flow AW/ W is shown for thecorresponding percentage change in adjustment AV/ V. Curves A and C showthe relationship for a valve embodying the invention while curves B andD show the relationship for a separate nozzle and throttling valve ofthe prior art. These comparative tests match performance curves forthese two types of valves in order to compare the full open gapnecessary to achieve similar results. The tests were made employinghighdensity polyethylene as the plastic melt material and resulted in thefollowing data:

Curve Gap A 0.278 in. 8 0.166 in. C 0.500 in. D 0.333 in.

This data shows that the larger gaps of the valve of the presentinvention permit less sensitive adjustment than those of the equivalentflow smaller gaps of prior art valves. Therefore, the valve of theinvention affords more throttling control.

zles depending on the adjustment of the annular gaps of the two nozzlevalves obtained by rotary screw adjustment of the valve stems.

The land length of the throttling surface on both valve stems was 1inch. The land area made a 45 angle with the axis of the valve stem andtapered from a maximum diameter of 2 inches to a minimum diameter of0.6255 inches which was the size of the passage in the valve stemthrough which the nozzle rod passes. The over-all size of the valve bodychamber was 2.5 inches in diameter and 1 9/16 inches in depth from theupper valve body to where the 45 tapered surface began. The nozzle rodwas 0.6245 inches in diameter and the passage was 0.6255 inches indiameter. The passage in the manifold as 1.5 inches in diameter and thepassage connecting the manifold to the valve chambers was threefourthsinch in diameter. The manifold and valve stem were constructed by steel,while the upper valve body and nozzle rod were constructed of bronzealloy.

in other operations, the valve was used to control the flow ofpolyethylene and other plastic melt materials.

What is claimed is:

l. A combined nozzle shut-off and flow control valve for use with aplastic molding machine comprising: a valve body having a bore includinga lower surface communicating with outlet passage means of reduceddiameter and axially aligned with said bore and radial inlet passagemeans; a valve stem, having an inner axial passage and having an outerlower surface, axially positioned within said bore and capable ofrelative axial movement therein; nozzle valve rod means slidablypositioned in said valve stem inner axial passage and aligned toregister in to effect closure of said outlet passage means; said lowersurfaces of said bore and said valve stem being parallel annularsurfaces providing a gap of variable width to effect flow controlthrough said valve.

2. The nozzle valve in accordance with claim 1, wherein an annularchamber is provided between said valve body bore and said valve stemwhich is in communication with said radial inlet passage means and saidgap of variable width.

3. The nozzle valve in accordance with claim 2, wherein said radialinlet passage terminates in an annular manifold chamber positionedbetween said valve body bore and said valve stem upstream of saidannular chamber.

1. A combined nozzle shut-off and flow control valve for use with aplastic molding machine comprising: a valve body having a bore includinga lower surface communicating with outlet passage means of reduceddiameter and axiAlly aligned with said bore and radial inlet passagemeans; a valve stem, having an inner axial passage and having an outerlower surface, axially positioned within said bore and capable ofrelative axial movement therein; nozzle valve rod means slidablypositioned in said valve stem inner axial passage and aligned toregister in to effect closure of said outlet passage means; said lowersurfaces of said bore and said valve stem being parallel annularsurfaces providing a gap of variable width to effect flow controlthrough said valve.
 2. The nozzle valve in accordance with claim 1,wherein an annular chamber is provided between said valve body bore andsaid valve stem which is in communication with said radial inlet passagemeans and said gap of variable width.
 3. The nozzle valve in accordancewith claim 2, wherein said radial inlet passage terminates in an annularmanifold chamber positioned between said valve body bore and said valvestem upstream of said annular chamber.